/Engine/Source/Editor/UnrealEd/Public/Editor.h
Delegate type for triggering when new actors are placed on to the viewport. Triggers before NewActorsDropped if placement is caused by a drop action
typedef TMulticastDelegate_TwoParams< void, [UObject](API\Runtime\CoreUObject\UObject\UObject) *, const [TArray](API\Runtime\Core\Containers\TArray)< [AActor](API\Runtime\Engine\GameFramework\AActor) * > & > FOnNewActorsPlaced